FWIW my guess is most people are aware, and do know that supermarket/drugstore acetaminophen / paracetamol is the same, in some relevant sense, as Tylenol / Panadol. It's not like the retailers lack marketing resources. But for these off-the-shelf drugs the total $/£ amounts are small for a lot of people.
Then, there _are_ arguments about whether generics face adequate testing to ensure the same quality as the originally-approved name brand drug. A lot of this is FUD - I'll happily buy generic acetaminophen in the US - but it's not a totally irrational concern. I doubt any regulator ensures generic equivalence to the same degree of conformity that a big pharma companies' own quality control does.
For example, I personally find real differences in the jankiness of different asthma inhalers, even amongst generics. Maybe that's because I don't shake/use/clean them exactly per the directions, but then that's real-world use for you. My personal experience says brand-name Ventolin has solved a "robustness against user error" problem in a way some alternatives often have not, suggesting the FDA does not enforce equivalence on this dimension. It's not enough of a difference for me to go name-brand, since out-of-pocket price differences can be egregious, but I do distinguish between otherwise-unknown generics.
Finally, you may trust the UK regulator and so do I, but traveling somewhere without good regulatory oversight, I'd probably reach for Panadol - assuming it seemed authentic - over a generic brand I'd never heard of. Brands have value and brand owners have a lot to lose, which is a kind of insurance (see 1982 Tylenol recall).